#include <iostream>
#include <string>
#include <map>
using namespace std;
#define DEBUG
inline int read()
{
    int c=getchar(), f=1, x=0;
    if(c=='-') f*=-1;
    while(c<'0'&&'9'<c) c=getchar();
    while('0'<=c&&c<='9') 
        x=(x<<3)+(x<<1)+c-'0', c=getchar();
    return x;
}

inline void write(int x)
{
    if(x>=10) write(x/10);
    putchar(x%10-'0');
}
const int N=60;
double val[N], f;
int n;
void solve()
{
    cin >> n >> f;
    for(int i=0; i<=n; i++)
        cin >> val[i];
    for(int i=n; i>0; i--)
        val[i-1]+=val[i]/(1+f);
    printf("%.3lf\n", val[0]);
}

signed main()
{
    #ifdef DEBUG
        freopen("../in.txt", "r", stdin);
        freopen("../out.txt", "w", stdout);
    #endif

    int T=1; //cin >> T; 
    while(T--) 
    {
        solve();
    }
    return 0;
}